1. Field of the Invention
The invention relates to compositions and methods for cleaning membranes used in separation facilities, such as facilities that clarify, concentrate and/or fractionate a variety of dairy products. The cleaning compositions can remove protein, fat, minerals, and other feed stream components, and offer an environmentally friendly alternative surfactant system to nonylphenol ethoxylates.
2. Description of the Related Art
The separation of dairy fluids using semi-permeable membranes has been used to clarify, concentrate and/or fractionate a variety of dairy products. However, membrane performance may decrease during processing of milk, whey, and other feed streams due to the fouling of the membrane surface or membrane pores by protein, fat, minerals, and other feed stream components. Fouling leads to a decline in flux with time of operation. Flux decline is typically a reduction in permeation flow or permeation rates that occurs when all operating parameters, such as pressure, feed flow rate, temperature, and feed concentration are kept constant. Membrane fouling is a complicated process and is believed to occur due to a number of factors including electrostatic attraction, hydrophobic and hydrophilic interactions, and the deposition and accumulation of feed components on the membrane surface and/or within the pores of the membrane. It is expected that almost all feed components will foul membranes to a certain extent. Fouling components and deposits can include inorganic salts, particulates, microbials and organics.
Filtration membranes typically require periodic cleaning to allow for successful use within separation facilities such as those found in the dairy industry. The filtration membranes can be cleaned by removing foreign material from the surface and body of the membrane and associated equipment. The cleaning procedure for filtration membranes can involve a clean-in-place process where cleaning agents are circulated over the membrane to wet, penetrate, dissolve and/or rinse away foreign materials from the membrane.
Nonylphenol ethoxylates (NPE) have played an important role in the cleaning and performance efficiency of membrane filtration systems utilized in dairy applications. NPE 9 (9 mole ethoxylate of nonyl phenol) and other phenol ethoxylates have been the standard surfactant used in the cleaning of most membrane systems. Membrane systems that have poor or unoptimized rinses can leave traces of surfactants behind. These surfactants can then become part of the product during processing. To verify potential surfactant contamination, testing of rinse waters will indicate if particular system has a problem with residual NPE.
Nonylphenols have been shown to be bio-accumulators and endocrine disruptors leading to pressure on NPE's by regulatory bodies in both the United States and the European Union. Current restrictions in place in the European Union has set a limit of 10 ppb in fractions from whey and milk separation. In the United States, starting in 2015 all manufacturers with have to report all quantities of NPE utilized.
Due to these restrictions, dairy producers are looking for alternative surfactant chemistries that provide the same cleaning performance as ethoxylated nonylphenols without the drawbacks that are associated with NPE's. Typically, alkylphenol ethoxylates have been components in cleaning formulations or additives to a cleaning program. These surfactants serve a twofold purpose; wetting surfaces and emulsification of dairy soils that typically build on membrane surfaces, and maintaining hydrophilic membrane surfaces to maintain flux efficiency. It is difficult to reproduce these properties with surfactants other than alkylphenol ethoxylates.
Thus, there exists a need for alternative surfactant technologies that do not suffer from the regulatory restrictions that plague nonylphenol ethoxylates and have acceptable performance with regards to membrane compatibility and membrane cleaning performance.